buffer.c

/*
 * Copyright (c) 2002, 2003 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#ifdef WIN32
#include <winsock2.h>
#include <windows.h>
#endif

#ifdef HAVE_VASPRINTF
/* If we have vasprintf, we need to define this before we include stdio.h. */
#define _GNU_SOURCE
#endif

#include <sys/types.h>

#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#ifdef HAVE_SYS_IOCTL_H
#include <sys/ioctl.h>
#endif

#include <assert.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_STDARG_H
#include <stdarg.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include "event.h"
#include "config.h"
#include "evutil.h"
#include "./log.h"

struct evbuffer*
evbuffer_new(void)
{
    struct evbuffer* buffer;

    buffer = calloc(1, sizeof(struct evbuffer));

    return (buffer);
}

void
evbuffer_free(struct evbuffer* buffer)
{
    if (buffer->orig_buffer != NULL)
        free(buffer->orig_buffer);
    free(buffer);
}

/*
 * This is a destructive add.  The data from one buffer moves into
 * the other buffer.
 */

#define SWAP(x,y) do { \
    (x)->buffer = (y)->buffer; \
    (x)->orig_buffer = (y)->orig_buffer; \
    (x)->misalign = (y)->misalign; \
    (x)->totallen = (y)->totallen; \
    (x)->off = (y)->off; \
} while (0)

int
evbuffer_add_buffer(struct evbuffer* outbuf, struct evbuffer* inbuf)
{
    int res;

    /* Short cut for better performance */
    // outbuf内存为0，直接交换即可
    if (outbuf->off == 0) {
        struct evbuffer tmp;
        size_t oldoff = inbuf->off;

        /* Swap them directly */
        SWAP(&tmp, outbuf);
        SWAP(outbuf, inbuf);
        SWAP(inbuf, &tmp);

        /*
         * Optimization comes with a price; we need to notify the
         * buffer if necessary of the changes. oldoff is the amount
         * of data that we transfered from inbuf to outbuf
         */
        if (inbuf->off != oldoff && inbuf->cb != NULL)
            (*inbuf->cb)(inbuf, oldoff, inbuf->off, inbuf->cbarg);
        if (oldoff && outbuf->cb != NULL)
            (*outbuf->cb)(outbuf, 0, oldoff, outbuf->cbarg);

        return (0);
    }

    res = evbuffer_add(outbuf, inbuf->buffer, inbuf->off);
    if (res == 0) {
        /* We drain the input buffer on success */
        evbuffer_drain(inbuf, inbuf->off);
    }

    return (res);
}

int
evbuffer_add_vprintf(struct evbuffer* buf, const char* fmt, va_list ap)
{
    char* buffer;
    size_t space;
    size_t oldoff = buf->off;
    int sz;
    va_list aq;

    /* make sure that at least some space is available */
    if (evbuffer_expand(buf, 64) < 0)
        return (-1);
    for (;;) {
        size_t used = buf->misalign + buf->off;
        buffer = (char*)buf->buffer + buf->off;
        assert(buf->totallen >= used);
        space = buf->totallen - used;

#ifndef va_copy
#define    va_copy(dst, src)    memcpy(&(dst), &(src), sizeof(va_list))
#endif
        va_copy(aq, ap);

        sz = evutil_vsnprintf(buffer, space, fmt, aq);

        va_end(aq);

        if (sz < 0)
            return (-1);
        if ((size_t)sz < space) {
            buf->off += sz;
            if (buf->cb != NULL)
                (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);
            return (sz);
        }
        if (evbuffer_expand(buf, sz + 1) == -1)
            return (-1);

    }
    /* NOTREACHED */
}

int
evbuffer_add_printf(struct evbuffer* buf, const char* fmt, ...)
{
    int res = -1;
    va_list ap;

    va_start(ap, fmt);
    res = evbuffer_add_vprintf(buf, fmt, ap);
    va_end(ap);

    return (res);
}

/* Reads data from an event buffer and drains the bytes read */

int
evbuffer_remove(struct evbuffer* buf, void* data, size_t datlen)
{
    size_t nread = datlen;
    if (nread >= buf->off)
        nread = buf->off;

    memcpy(data, buf->buffer, nread);
    evbuffer_drain(buf, nread);

    return (nread);
}

/*
 * Reads a line terminated by either '\r\n', '\n\r' or '\r' or '\n'.
 * The returned buffer needs to be freed by the called.
 */

char*
evbuffer_readline(struct evbuffer* buffer)
{
    u_char* data = EVBUFFER_DATA(buffer);
    size_t len = EVBUFFER_LENGTH(buffer);
    char* line;
    unsigned int i;

    for (i = 0; i < len; i++) {
        if (data[i] == '\r' || data[i] == '\n')
            break;
    }

    if (i == len)
        return (NULL);

    if ((line = malloc(i + 1)) == NULL) {
        fprintf(stderr, "%s: out of memory\n", __func__);
        return (NULL);
    }

    memcpy(line, data, i);
    line[i] = '\0';

    /*
     * Some protocols terminate a line with '\r\n', so check for
     * that, too.
     */
    if ( i < len - 1 ) {
        char fch = data[i], sch = data[i + 1];

        /* Drain one more character if needed */
        if ( (sch == '\r' || sch == '\n') && sch != fch )
            i += 1;
    }

    evbuffer_drain(buffer, i + 1);

    return (line);
}

char*
evbuffer_readln(struct evbuffer* buffer, size_t* n_read_out,
                enum evbuffer_eol_style eol_style)
{
    u_char* data = EVBUFFER_DATA(buffer);
    u_char* start_of_eol, *end_of_eol;
    size_t len = EVBUFFER_LENGTH(buffer);
    char* line;
    unsigned int i, n_to_copy, n_to_drain;

    if (n_read_out)
        *n_read_out = 0;

    /* depending on eol_style, set start_of_eol to the first character
     * in the newline, and end_of_eol to one after the last character. */
    switch (eol_style) {
        // \r 或者 \n 被作为换行处理，都会被移除比如
        // aaa\r\r\n\nbbbb   -> aaa  NULL
        // aaaa\r\n\nbbb\r\n -> aaa bbb
        // \r\r\aaa\nbbb     -> "" aaa NULL
    case EVBUFFER_EOL_ANY:
        for (i = 0; i < len; i++) {
            if (data[i] == '\r' || data[i] == '\n')
                break;
        }
        if (i == len)
            return (NULL);
        start_of_eol = data + i;
        ++i;
        for ( ; i < len; i++) {
            if (data[i] != '\r' && data[i] != '\n')
                break;
        }
        end_of_eol = data + i;
        break;
        // 处理 \r\n 或者 \n，比如
        // aaa\r\nbbb\r\n -> aaa bbb
        // \naaa\nbbb -> "" aaa NULL
    case EVBUFFER_EOL_CRLF:
        end_of_eol = memchr(data, '\n', len);
        if (!end_of_eol)
            return (NULL);
        if (end_of_eol > data && *(end_of_eol - 1) == '\r')
            start_of_eol = end_of_eol - 1;
        else
            start_of_eol = end_of_eol;
        end_of_eol++; /*point to one after the LF. */
        break;
        // \r\n作为换行
    case EVBUFFER_EOL_CRLF_STRICT: {
        u_char* cp = data;
        while ((cp = memchr(cp, '\r', len - (cp - data)))) {
            if (cp < data + len - 1 && *(cp + 1) == '\n')
                break;
            if (++cp >= data + len) {
                cp = NULL;
                break;
            }
        }
        if (!cp)
            return (NULL);
        start_of_eol = cp;
        end_of_eol = cp + 2;
        break;
    }
    // \n 作为换行
    case EVBUFFER_EOL_LF:
        start_of_eol = memchr(data, '\n', len);
        if (!start_of_eol)
            return (NULL);
        end_of_eol = start_of_eol + 1;
        break;
    default:
        return (NULL);
    }

    n_to_copy = start_of_eol - data;
    n_to_drain = end_of_eol - data;

    if ((line = malloc(n_to_copy + 1)) == NULL) {
        event_warn("%s: out of memory\n", __func__);
        return (NULL);
    }

    memcpy(line, data, n_to_copy);
    line[n_to_copy] = '\0';

    evbuffer_drain(buffer, n_to_drain);
    if (n_read_out)
        *n_read_out = (size_t)n_to_copy;

    return (line);
}

/* Adds data to an event buffer */
// 调整内存，将buffer前移的数据放到前面，这样可以充分利用已经被移除
// 的内存，但是需要将后面的内存前向拷贝
static void
evbuffer_align(struct evbuffer* buf)
{
    memmove(buf->orig_buffer, buf->buffer, buf->off);
    buf->buffer = buf->orig_buffer;
    buf->misalign = 0;
}

#ifndef SIZE_MAX
#define SIZE_MAX ((size_t)-1)
#endif

/* Expands the available space in the event buffer to at least datlen */
// 扩充datlen大小的内存
int
evbuffer_expand(struct evbuffer* buf, size_t datlen)
{
    size_t used = buf->misalign + buf->off;
    size_t need;

    assert(buf->totallen >= used);

    /* If we can fit all the data, then we don't have to do anything */
    // 如果有datlen大小的内存可用，那么就不扩充
    if (buf->totallen - used >= datlen)
        return (0);
    /* If we would need to overflow to fit this much data, we can't
     * do anything. */
    if (datlen > SIZE_MAX - buf->off)
        return (-1);

    /*
     * If the misalignment fulfills our data needs, we just force an
     * alignment to happen.  Afterwards, we have enough space.
     */
    // 剩余内存足够datlen的话，只需要将后面的内存往上移就能满足
    // totallen-off包括了废弃的前面部分内存后没有使用的内存
    if (buf->totallen - buf->off >= datlen) {
        evbuffer_align(buf);
    } else {
        void* newbuf;
        size_t length = buf->totallen;
        size_t need = buf->off + datlen; // 需要申请的内存大小

        if (length < 256)
            length = 256;
        if (need < SIZE_MAX / 2) {
            while (length < need) {
                length <<= 1;
            }
        } else {
            length = need;
        }

        if (buf->orig_buffer != buf->buffer)
            evbuffer_align(buf);
        if ((newbuf = realloc(buf->buffer, length)) == NULL)
            return (-1);

        buf->orig_buffer = buf->buffer = newbuf;
        buf->totallen = length;
    }

    return (0);
}

int
evbuffer_add(struct evbuffer* buf, const void* data, size_t datlen)
{
    size_t used = buf->misalign + buf->off;
    size_t oldoff = buf->off;

    if (buf->totallen - used < datlen) {
        if (evbuffer_expand(buf, datlen) == -1)
            return (-1);
    }

    memcpy(buf->buffer + buf->off, data, datlen);
    buf->off += datlen;

    if (datlen && buf->cb != NULL)
        (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

    return (0);
}

// 放弃buf前面len字节大小的内存
void
evbuffer_drain(struct evbuffer* buf, size_t len)
{
    size_t oldoff = buf->off;

    if (len >= buf->off) {
        buf->off = 0;
        buf->buffer = buf->orig_buffer;
        buf->misalign = 0;
        goto done;
    }
    // 前移
    buf->buffer += len;
    buf->misalign += len;
    // 可用内存相应减少
    buf->off -= len;

done:
    /* Tell someone about changes in this buffer */
    if (buf->off != oldoff && buf->cb != NULL)
        (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

}

/*
 * Reads data from a file descriptor into a buffer.
 */

#define EVBUFFER_MAX_READ    4096

int
evbuffer_read(struct evbuffer* buf, int fd, int howmuch)
{
    u_char* p;
    size_t oldoff = buf->off;
    int n = EVBUFFER_MAX_READ;

#if defined(FIONREAD)
#ifdef WIN32
    long lng = n;
    if (ioctlsocket(fd, FIONREAD, &lng) == -1 || (n = lng) <= 0) {
#else
    if (ioctl(fd, FIONREAD, &n) == -1 || n <= 0) {
#endif
        n = EVBUFFER_MAX_READ;
    } else if (n > EVBUFFER_MAX_READ && n > howmuch) {
        /*
         * It's possible that a lot of data is available for
         * reading.  We do not want to exhaust resources
         * before the reader has a chance to do something
         * about it.  If the reader does not tell us how much
         * data we should read, we artifically limit it.
         */
        if ((size_t)n > buf->totallen << 2)
            n = buf->totallen << 2;
        if (n < EVBUFFER_MAX_READ)
            n = EVBUFFER_MAX_READ;
    }
#endif
    if (howmuch < 0 || howmuch > n)
        howmuch = n;

    /* If we don't have FIONREAD, we might waste some space here */
    if (evbuffer_expand(buf, howmuch) == -1)
        return (-1);

    /* We can append new data at this point */
    p = buf->buffer + buf->off;

#ifndef WIN32
    n = read(fd, p, howmuch);
#else
    n = recv(fd, p, howmuch, 0);
#endif
    if (n == -1)
        return (-1);
    if (n == 0)
        return (0);

    buf->off += n;

    /* Tell someone about changes in this buffer */
    if (buf->off != oldoff && buf->cb != NULL)
        (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

    return (n);
}

int
evbuffer_write(struct evbuffer* buffer, int fd)
{
    int n;

#ifndef WIN32
    n = write(fd, buffer->buffer, buffer->off);
#else
    n = send(fd, buffer->buffer, buffer->off, 0);
#endif
    if (n == -1)
        return (-1);
    if (n == 0)
        return (0);
    evbuffer_drain(buffer, n);

    return (n);
}

u_char*
evbuffer_find(struct evbuffer* buffer, const u_char* what, size_t len)
{
    u_char* search = buffer->buffer, *end = search + buffer->off;
    u_char* p;

    while (search < end &&
           (p = memchr(search, *what, end - search)) != NULL) {
        if (p + len > end)
            break;
        if (memcmp(p, what, len) == 0)
            return (p);
        search = p + 1;
    }

    return (NULL);
}

void evbuffer_setcb(struct evbuffer* buffer,
                    void (*cb)(struct evbuffer*, size_t, size_t, void*),
                    void* cbarg)
{
    buffer->cb = cb;
    buffer->cbarg = cbarg;
}